Question: ${1 \div 0.4 = {?}}$
Explanation: $ {1 \div 0.4 = 1 \div \dfrac{4}{10}} $ $ {\phantom{1 \div 0.4} = 1 \div \dfrac{2}{5}} $ Dividing by a fraction is the same as multiplying by the reciprocal of the fraction. $ {1 \div \dfrac{2}{5} = 1 \times \dfrac{5}{2}} $ $ {\phantom{1 \div \dfrac{2}{5}} = \dfrac{1 \times 5}{2}} $ $ {\phantom{1 \div \dfrac{2}{5}} = \dfrac{5}{2}} $ $ {\phantom{1 \div \dfrac{2}{5}} = 2.5} $